Method of processing discarded seatbelt pretensioner

ABSTRACT

The present invention provides a highly workable disposal method for a seatbelt pretensioner used in an automobile. This method is a disposal method for a seatbelt pretensioner and attachments thereof, in which the attachments are removed, whereupon the seatbelt pretensioner, which contains an explosive component, is subjected to thermal treatment at a temperature that is equal to or greater than the ignition point of the explosive component.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a disposal method for a seatbeltpretensioner attached to a seatbelt of an automobile.

Prior Art

A seatbelt is attached to an automobile to protect a passenger fromimpact during a collision, and a seatbelt pretensioner (a deviceattached with a gas generator containing an ignition charge and a gasgenerating agent for tightening the seatbelt) is attached to theseatbelt as means for tightening the seatbelt to protect the passengerwhen the automobile collides.

It is predicted that in the future, more and more automobiles comprisinga seatbelt pretensioner that contains an ignition charge and a gasgenerating agent will be discarded, and therefore, from the viewpointsof safety and effective utilization of resources, it is necessary totreat the ignition charge and gas generating agent safely to recovermetals and the like therefrom.

During treatment of a seatbelt pretensioner, it is necessary to activatethe installed ignition charge and gas generating agent throughhigh-temperature treatment, recover and reuse usable resources such asmetals, and also to ensure safety during the treatment such that noharmful substances are generated.

JP-A No. 11-101422 may be cited as prior art relating to the presentinvention.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a seatbelt pretensionerdisposal method with which a seatbelt pretensioner can be treated safelyand efficiently during the disposal of an automobile or the like, andwhich facilitates the recovery and reuse of usable materials.

As means for achieving this object, the present invention provides aseatbelt pretensioner disposal method for a seatbelt pretensioner andattachments thereof, wherein the seatbelt pretensioner, which containsan explosive component, and the attachments thereof, are subjected tothermal treatment at a temperature that is equal to or higher than anignition point of the explosive component.

As further means for achieving this object, the present inventionprovides a seatbelt pretensioner disposal method for a seatbeltpretensioner and attachments thereof, wherein the seatbelt pretensioner,which contains an explosive component, is subjected to thermal treatmentat a temperature that is equal to or higher than an ignition point ofthe explosive component after removing the attachments.

As further means for achieving this object, the present inventionprovides a seatbelt pretensioner disposal method for a seatbeltpretensioner and attachments thereof, wherein only a part containing anexplosive component is removed from the seatbelt pretensioner, and thispart is subjected to thermal treatment at a temperature that is equal toor higher than an ignition point of the explosive component.

The explosive component of the present invention includes both anignition charge for igniting a gas generating agent and a gas generatingagent for generating a gas.

The seatbelt pretensioner is attached to an automobile together with aseatbelt and a retractor attached with a fixing buckle, and therefore,when removed from a discarded vehicle, the seatbelt pretensioner,seatbelt, fixing buckle, and retractor are removed in integral form.Accordingly, the attachments of the present invention denote the partsother than the seatbelt pretensioner, i.e. the seatbelt, fixing buckle,and retractor.

The seatbelt pretensioner and attachments serving as the treatmentsubjects of the present invention comprise all components that need tobe treated for a variety of reasons, for example defective goodsproduced during the manufacturing process, goods returned from theautomobile maker, inventory goods that are no longer in production, andseatbelt pretensioners removed from discarded vehicles. Note thatdefective goods produced during the manufacturing process, goodsreturned from the automobile maker, and inventory goods that are nolonger in production include seatbelt pretensioners without attachments.

According to the seatbelt pretensioner disposal method of the presentinvention, treatment can be performed safely and efficiently, thegeneration of harmful substances such as dioxins can be suppressedgreatly, and the recovery and reuse of usable materials can befacilitated.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a view illustrating a treatment method of the presentinvention.

Explanation of Numerals

-   10 thermally treating tower-   12 seatbelt pretensioner introducing port-   14 combustion furnace-   16 exhaust gas tube-   17 cooling tower

PREFERRED EMBODIMENTS OF THE INVENTION

A seatbelt pretensioner disposal method of the present invention will bedescribed using FIG. 1. FIG. 1 illustrates thermally treating equipmentthat may also be applied to the treatment of inflators for various typesof air bags, comprising a thermally treating tower, an introducing portfor introducing a seatbelt pretensioner into the thermally treatingtower, a heating device disposed within the thermally treating tower,and a cooling device for cooling gas that is discharged from thethermally treating tower.

First, in a case where the seatbelt pretensioner is formed integrallywith attachments, the attachments, constituted by a seatbelt, a fixingbuckle, and a retractor, are removed as preliminary processing forthermally treating the seatbelt pretensioner.

Note that the seatbelt pretensioner is constituted by a main bodyportion and a micro gas generator (abbreviated to MGG) accommodating anignition charge and a gas generating agent, and therefore such a methodmay be employed that the main body portion and MGG are separated fromeach other, the MGG alone is subjected to thermal treatment, and themain body portion is subjected to separation and recovery processingtogether with the attachments.

Once the attachments and MGG have been removed, the seatbeltpretensioner is separated into plastic and metal types. The plastic maybe separated into thermoplastic resins and thermosetting resins, or maybe separated according to the material of the plastic. The seatbeltpretensioner often contains metals such as iron, stainless steel, zincalloy, and aluminum, and therefore it is important to conduct theseparation operation with a view to recycling valuable resources.

Next, the seatbelt pretensioner, having undergone preliminary processingif necessary, is introduced into the thermally treating tower, where theprocessing of a thermal treatment step is performed at a temperaturewhich burns the ignition charge and gas generating agent in the seatbeltpretensioner, but does not melt the metals constituting the seatbeltpretensioner.

As shown in FIG. 1, for example, it is desirable that a thermallytreating tower 10 form an entire, single treatment system (thermallytreating equipment) together with an exhaust gas tube 16, a seatbeltpretensioner introducing port 12, a combustion furnace (for example, acombination of a high-calorie burner and a low-calorie burner) 14, anexhaust gas cooling tower 17, an exhaust gas cooling shower 19, acooling tower tank 18, and a gas discharge tube 26, all of which areannexed to the thermally treating tower 10. The reference numerals 13and 25 denote metal gratings or the like formed from wire mesh, punchedmetal, iron, or similar, the reference numeral 20 denotes a heatexchanger, the reference numeral 22 denotes a cooling tower, and thereference numeral 24 denotes a pump. Note that a metal partition wall 11(see FIG. 1) which exhibits the same action (protecting the inner wallof the thermally treating tower 10) as a device disclosed in FIG. 1 andso on of JP-A No. 11-101422, may be provided inside the thermallytreating tower 10. Other devices or systems may be combined with thesystem shown in FIG. 1 as required.

Having been introduced into the thermally treating tower 10 through theseatbelt pretensioner introducing port 12, a seatbelt pretensioner 30 isheated to at least a predetermined temperature such that the ignitioncharge and gas generating agent therein are ignited and burned. Thethermal treatment temperature in the thermally treating tower 10 is setsuch that the ignition charge and gas generating agent inside theseatbelt pretensioner 30 burn but the metals constituting the seatbeltpretensioner 30 do not melt.

The temperature at which the gas generating agent burns is equal to orgreater than the ignition point of the ignition charge and gasgenerating agent. The ignition point differs according to thecomposition of the ignition charge and gas generating agent. Theignition point of a typical ignition charge or gas generating agent isapproximately 150 to 500° C., but at excessively high temperatures, theinner wall of the thermally treating tower 10 may be damaged, andtherefore the temperature in the interior of the thermally treatingtower 10 is preferably in the range of 150 to 700° C.

The temperature at which the main metals constituting the seatbeltpretensioner do not melt depends on the material of the seatbeltpretensioner. However, these metals are typically aluminum, iron, andstainless steel, and therefore a temperature which is lower than themelting temperature of these metals serves as a maximum temperature. Inthe case of aluminum, a temperature range of 450 to 550° C. ispreferable, whereas in the case of iron and stainless steel, atemperature range of 550 to 700° C. is preferable. As noted above, it isalso desirable that prevention of heat damage to the thermally treatingtower 10 be taken into consideration.

The combustion gas is discharged through the exhaust gas tube 16connected to a ceiling portion of the thermally treating tower 10,cooled in the cooling tower 17 by a water spray produced by the coolingshower 19, and then led into water contained in the cooling tower tank18. The gas that accumulates inside the cooling tower tank 18 isdischarged into the atmosphere through the gas discharge tube 26.

In the thermal treatment performed in the thermally treating tower 10,the internal temperature of the thermally treating tower 10 ispreferably raised in advance, using the combustion furnace 14, to atemperature at which the ignition charge and gas generating agent insidethe seatbelt pretensioner 30 burns but the metals constituting theseatbelt pretensioner 30 do not melt (in the case of aluminum, about500° C.) and then maintained at that temperature. A method in which thehigh-calorie burner and low-calorie burner are burned simultaneously,the high-calorie burner is halted when the predetermined temperature isreached, and only the low-calorie burner is burned thereafter, may beapplied as this temperature raising and maintaining method. At thistime, the amount of air blown into the thermally treating tower 10 maybe adjusted accordingly.

After the seatbelt pretensioner 30 is introduced into the thermallytreating tower 10, the predetermined temperature is maintained untiltreatment of the seatbelt pretensioner 30 is complete. Likewise in acase where a plurality of seatbelt pretensioners 30 is introduced inseveral batches and treated in order of introduction, measures are takento ensure that the predetermined temperature is maintained untiltreatment of the seatbelt pretensioner 30 introduced last is complete.

If the combustion furnace 14 is halted immediately after the seatbeltpretensioner 30 is introduced, treatment of the seatbelt pretensioner(combustion processing of the ignition charge and gas generating agent)may be insufficient, and hence the temperature management describedabove is preferably performed to prevent the occurrence of such asituation.

The duration period of the predetermined temperature during the thermaltreatment process is determined in advance by confirming one or both ofan amount of time required for all of the ignition charge, gasgenerating agent, or other agent in the seatbelt pretensioner to beactivated, which is determined by means of a thermal stability test inwhich the seatbelt pretensioner is exposed to an atmosphere having thetemperature at which the seatbelt pretensioner is to be treated in thethermally treating tower 10, and an amount of time required for theseatbelt pretensioner to be treated, which is determined by means of abonfire test performed on the seatbelt pretensioner (in which theseatbelt pretensioner is exposed to a flame and the state of theseatbelt pretensioner is observed). The predetermined temperatureduration period is set at least equal to or longer than a period inwhich the seatbelt pretensioner can be treated.

To ensure that the seatbelt pretensioner is activated reliably, theduration period of the predetermined temperature during the thermaltreatment process is preferably set between one and one hundred timesthe time required to complete treatment of the seatbelt pretensionerfollowing introduction thereof, or following introduction of the finalseatbelt pretensioner when a plurality of seatbelt pretensioners isintroduced in several batches, and more preferably between three andthirty times this time.

Alternatively, treatment in the thermally treating tower 10 may beperformed using a method in which the internal temperature of thethermally treating tower 10 is raised in advance to a temperature nearthe ignition point of the ignition charge and gas generating agent, theseatbelt pretensioner 30 is introduced therein, and then the temperatureis raised at once, or a method in which the internal temperature of thethermally treating tower 10 is held at normal temperature or atemperature that is considerably lower than the ignition point of theignition charge and gas generating agent, the seatbelt pretensioner 30is introduced therein, and then the temperature is raised gradually.

Note that during thermal treatment in the thermally treating tower 10,the pressure generated during combustion of the ignition charge and gasgenerating agent may act as thrust which propels the seatbeltpretensioner 30. However, the partition means 25 formed from wire mesh,punched metal, a metal grating, or similar are attached removablybetween the thermally treating tower 10 and the exhaust gas tube 16, andtherefore the seatbelt pretensioner 30 is prevented from flying out ofthe thermally treating tower 10. The partition means 25 are attachedremovably using a bolt and nut in a flange portion provided on an innerwall surface 10 a of the thermally treating tower 10 or an inner wallsurface 16 a of the exhaust gas tube 16. Further, by providing thepartition means 13 between the thermally treating tower 10 andcombustion furnace 14 to perform a similar function to the partitionmeans 25, the seatbelt pretensioner 30 is prevented from flying into thecombustion furnace 14.

The processes performed prior to thermal treatment are preferablyperformed in an indoor facility comprising a lightning conductor toprevent the seatbelt pretensioner from malfunctioning prior to treatmentin the event of a lightning strike. For the same reason, when storingthe seatbelt pretensioner temporarily prior to treatment, the seatbeltpretensioner is preferably stored in an indoor facility comprising alightning conductor.

Following the thermal treatment described above, the metals and othervaluable resources contained in the combustion residue are preferablyseparated and recovered together with or separately from theattachments.

EXAMPLE

The present invention will now be described in more detail on the basisof an example. However, the present invention is not limited to or bythis example.

Example 1

A seatbelt pretensioner and its attachments, obtained during thedemolition of a discarded vehicle, are formed integrally, and thereforethe attachments, constituted by a seatbelt, a fixing buckle, and aretractor, were removed, leaving a metal component (the seatbeltpretensioner) including an MGG.

Next, the seatbelt pretensioner including the MGG (outer diameter: 17mm; height: 31.5 mm in columnar form; outer shell container is formedfrom aluminum with a melting point of 660° C.; ignition charge isconstituted by zirconium/potassium perchlorate with an ignition point of491° C.; gas generating agent is constituted by 0.85 g of a substancecontaining cellulose nitrate and potassium nitrate, with an ignitionpoint between 160 and 180° C.) was subjected to thermal treatment.

The combustion furnace 14 was activated, whereby the internaltemperature of the thermally treating tower 10 was raised in advance to,and maintained at, approximately 500° C. In this temperature atmosphere,a total of two hundred seatbelt pretensioners 30 were introduced intothe thermally treating tower 10 through the seatbelt pretensionerintroducing port 12 in ten batches at six-minute intervals. Followingintroduction of the tenth batch of seatbelt pretensioners 30, theinternal temperature of the thermally treating tower 10 was maintainedat 500° C. for approximately 25 minutes. Note that the time required totreat twenty seatbelt pretensioners 30 was determined, as a result ofexperiment, to be between 114 and 484 seconds, and thereforehigh-temperature treatment of the inflator 30 was completed bymaintaining the interior of the thermally treating tower 10 at thepredetermined temperature for approximately 6 to 24 minutes.

The gas generating agent in the seatbelt pretensioner 30 was ignited andburned, and the gas produced by this combustion was discharged to thecooling tower 17 through the exhaust gas tube 16. The gas was cooled inthe cooling tower 17 by a water spray produced by the cooling shower 19,and then led into the water inside the cooling tower tank 18. Theaccumulated gas inside the cooling tower tank 18 was discharged into theatmosphere through the gas discharge tube 26. The temperature of the gasat the time of discharge was approximately 50° C.

When the gas inside the exhaust gas tube 16 was extracted and measured,the dioxin concentration thereof was found to be not more than 0.15ng-TEQ/Nm³. Analysis was performed in accordance with the “DioxinsMeasurement Manual In Waste Matter Treatment”, prepared by the WasteManagement Section of the Water Supply and Environmental SanitationDepartment in the Environmental Health Bureau of the Japanese Ministryof Health and Welfare.

1. A seatbelt pretensioner disposal method for a seatbelt pretensionerand attachments thereof, wherein the seatbelt pretensioner, whichcontains an explosive component, and the attachments thereof, aresubjected to thermal treatment at a temperature that is equal to orhigher than an ignition point of the explosive component.
 2. A seatbeltpretensioner disposal method for a seatbelt pretensioner and attachmentsthereof, wherein the seatbelt pretensioner, which contains an explosivecomponent, is subjected to thermal treatment at a temperature that isequal to or higher than an ignition point of the explosive componentafter removing the attachments.
 3. A seatbelt pretensioner disposalmethod for a seatbelt pretensioner and attachments thereof, wherein onlya part containing an explosive component is removed from the seatbeltpretensioner, and this part is subjected to thermal treatment at atemperature that is equal to or higher than an ignition point of theexplosive component.
 4. The seatbelt pretensioner disposal methodaccording to claim 1, wherein valuable resources, including metals, areseparated and recovered from combustion residue produced by the thermaltreatment.
 5. The seatbelt pretensioner disposal method according toclaim 1, wherein the removed attachments and/or the seatbeltpretensioner that remains after removal of the part containing theexplosive component are further dismantled, whereby plastics and metalsare separated and recovered according to type.
 6. The seatbeltpretensioner disposal method according to claim 1, wherein processingprior to the thermal treatment or storage of the seatbelt pretensionerprior to the thermal treatment is performed in an indoor facilitycomprising a lightning conductor.
 7. The seatbelt pretensioner disposalmethod according to claim 1, wherein the seatbelt pretensioner istreated using thermally treating equipment comprising a thermallytreating tower, a seatbelt pretensioner introducing port for introducingthe seatbelt pretensioner into the thermally treating tower, a heatingdevice disposed in the interior of the thermally treating tower, and acooling device for cooling gas that is discharged from the thermallytreating tower.